Bluetooth® (BT) carries two types of traffic: high priority traffic, for example, voice traffic, and low priority traffic. Low priority traffic is carried over Asynchronous Connectionless (ACL) links with retransmission capability.
Consider a device that has a BT functional module and a wireless local area network (WLAN) functional module. These two functional modules share access to a single wireless medium, because they both operate in the ISM 2.4 GHz band. To reduce the incidence of collisions, an arbitration mechanism, usually implemented as part of the WLAN functional module, determines which of the two functional modules is offered access to the shared wireless medium. Some arbitration mechanisms rely on packet counters and timeout intervals, offering access to one of the functional modules until it either completes a pre-specified number of packet exchanges or until a timer expires, before offering access to the other of the functional modules. Thus the BT functional module has reduced access to the wireless medium, due to sharing with the WLAN functional module. However, when the WLAN functional module is active, typically this is the result of being in an active WLAN network, which is more likely to result in additional interference to the BT functional module, thus increasing the need for more retransmissions of low priority BT traffic.